General venous disease affects almost 30% of the US adult population, with incidence increasing as the population ages. Of this population, approximately 2-5% have problems with venous valve incompetence, referred to as Chronic Venous Insufficiency (CVI), which lead to serious conditions including venous ulcers requiring long term treatment with only limited success.
The venous valves are bicuspid valves found primarily in the lower limbs; these act as one-way pressure regulators to ameliorate the effects of gravity-induced hydrostatic blood pressure, especially in the standing position where pressures of over 90 mm Hg can be experienced. Incompetence of these valves can be caused by a variety of factors related to aging, diabetes and hypertension, including deep vein thrombosis, etc. The primary means of treating venous valve incompetence currently involve external lower-limb constriction via a tight-fitting “sock” worn over the lower limb and knee or surgical reconstruction or replacement of the veins in cases of significant deterioration. Both methods are prone to significant problems. The “sock” method is not fully effective since the levels of pressure required to sufficiently compress a deep vein located within strong skeletal musculature are usually far too high to be well-tolerated. Further, patient compliance with this method is usually poor. The surgical reconstruction method may produce good results but is highly invasive, which can be problematic given the typically older and frailer patient that manifests this disease, and expensive.
The most intensive treatment need is for patients with non-healing, chronic venous ulcers. It has been estimated that 2.5 million people have CVI in the United States, and of those, 20% develop venous ulcers. Annually, approximately 1 million procedures for venous ulceration involving large deep veins and deep vein thrombosis are performed in the US. The number of procedures is expected to grow at double-digit rates over the next 10 years. However, the overall prognosis of venous ulcers is poor, with delayed healing and recurrent ulceration being common. More than 50% of venous ulcers require prolonged therapy lasting up to a year or more representing a significant burden on patients, care-givers, and insurers.
The socioeconomic impact of venous ulceration is dramatic, resulting in an impaired ability to engage in social and occupational activities, thus reducing the quality of life and imposing financial constraints. Disability related to venous ulcers leads to loss of productive work hours, estimated at 2 million workdays/year, and may cause early retirement, which is found in up to 12.5% of workers with venous ulcers. The financial burden of venous ulcer disease on the healthcare system is readily apparent. An estimated $1 billion is spent annually on the treatment of chronic wounds in the United States, or up to 2% of the total healthcare budget in all Western countries, and recent estimates place the cost of venous ulcer care at $3 billion annually.
The information included in this Background section of the specification, including any references cited herein and any description or discussion thereof, is included for technical reference purposes only and is not to be regarded subject matter by which the scope of the invention is to be bound.